Pulverized-coal-burning apparatus



3 Sheets-Sheet l y fi N W i: fi N xi q 9 mm on R w m a, M a P i! M WM 3 km P. C. MULLIGAN ET AL PULVERIZED COAL BURNING APPARATUS Filed Feb. 16

Get. 7 1924.

Oct. 7 1924. 1,510,693

P. C. MULLIGAN ET AL PULVERIZED COAL BURNING APPARATUS Filed Feb. 16. '1921 5 Sheets-Sheets AT RNEYS r FREDERICK S. BRINT'ON,

PAUL C. MULLIGAN, FREDERICK S. BRINTON, AND HELMUTH W. SCHMITZ, OF

SEATTLE, WASHINGTON, ASSIGNORS TO PULVERIZED COAL EQUIPMENT CORPORA- TIQN, 0F SEATTLE, WASHINGTON, A CORPORATION OF WASHINGTON.

PULVERIZED-COAL-BURN IN G APPARATUS.

Application filed. February 16, 1921. Serial No. 445,367.

To all whom it may concern:

Be it known that we, PAUL O. MULmoAN, and HELMUTH W. SoHMrrz, all citizens of the United States, and residents of the city of Seattle, in the county of King and State of Washington, have invented certain new and useful Improvements in Pulverized-Coal-Burning Apparatus, of which the following is a specification.

Our invention relates to apparatus adapted for handling and treating all kinds of granular material, and particularly to apparatus which will operate continuously todry and advance finely divided particles of coal and like fuel to adapt it to be burned.

The principal object of our invention is, broadly, to produce a fuel burning apparatus which will operate upon finely divided or granular fuel to dry it so that it can be readily reduced to a pulverulent form in which it can be easily handled and burned.

Another'object is to provide a drier for use with such a fuel burner, or which may be used for drying grains or other granular material, which will advance the material being dried in a thin film, and which will agitate it to permit its being dried by the passage thereover of a current of drying air.

Another object is to produce an elevator for use in such a drier which is compact, rapid, and efiicient in operation, and in which the feed may be varied at will.

Summed up, our general object is to provide a compact, sensitive, easily adjustable and simply operable means for drying continuously non-fluid fuels so that by the use of other continuously operating apparatus it may be delivered continuously for burning in a pulverulent form.

Our invention comprises those novel parts and combinations thereof which are shown in the accompanying drawings, described in the specification, and particularly defined I by the claims terminating the same.v

In the accompanying drawings our invention and the several parts thereof are shown in the forms which are now preferred y us.

1 Figure 1 is an elevation showing generally the arrangement and combination of'parts which constitute our invention, in connection with an ordinary boiler.

Figure 2 is an axial section, with parts Figure 2, illustrating an elevating meansand fan such as we now in connection therewith. I

Figure 4 is an elevation of the control means for the elevator and drier, these beprefer to employ ing the means which control the amount of.

fuel passing through the apparatus, and fed to the burner.

Figure 5 is an end elevationof the same control means.

It is our intention to produce means for burning quite finely divided fuel without employing a grate, to be burned preferably from a blast burner in a pulverized form. Our apparatus, as at present designed, will operate upon coal of a size to pass through a quarter inch or three-eighthsinch mesh, and from that size downward. It has been diflicult to provide efficient means for burning such finely divided fuel, and in the past this has been largely discarded as screenings, the larger coalonly being used.

Our invention as at present designed is particularly for use upon shipboard where floor space is at a premium and where it is desirable to reduce the extent of fuel handling apparatus to the smallest possible minimum. It has been difficult heretofore V to provide suitable means for handling, drying and burning screenings aboard ship, for the reason that such apparatus required too much space. For a certain commercial installation designed to be employed in connection with a common type of marine steam plant developing 250 H. P. the floor space required for our fuel handling apparatus is only 8 feet square, this including the power unit for operating the fuel handling apparatus. Moreover, but 4% of the developed power is required in operating the entire fuel handling unit, which compares favorably with the best fuel oil burning apparatus. Further, on account of the danger of explosion or spontaneous ignition resulting from the storage and use of pulverized coal, its use aboard ships has been largely discontinued, and is looked upon with disfavor. It can thus be seen that b reducing the floor space, increasing the e ficiency, and in making use of a hitherto discarded fuel, our invention constitutes a dis tinct advance in the art.

A general typical arrangement of our apparatus is best shown in Figure 1. The fuel is first fed into a hopper H and from there it is delivered by suitable feed means into a drier D. During the course of the drying operation the fuel is elevated and is received in a second fuel-receiving hopper F at the upper end of the drier D. From there it is delivered by a conduit 0 by gravity to a pulverizer P. After being pulverized the fuel is picked up by a suction means J and carried into the conduit K, and is delivered to the burner B, which projects into the furnace A of the boiler S.

Air for drying the fuel may be led from a jacket L surrounding the base of the stack M by a pipe I to the hopper F, or to some other convenient entrance into the drier D. After passing through the drier the air, which by this time will contain considerable coal dust, may then be led by an outlet pipe 0 to the furnace A or in some other manner delivered to be burned and to dispose of the fuel particles thus carried by the drying medium without loss. Between 25 and 50 cubic feet of air is ordinarily required for drying one pound of coal, this depending upon the coal and its condition, and upon the humidity and temperature of the air. This is about oneseventh of the amountof air required for the complete combustion of the same coal. Instead (rf employing warm air from the jacket L, we may at times prefer to employ cool air, it having been shown that under certain conditions cool air has a greater drying effect than warm air. Power to operate the drier and pulverizer described may be supplied from a suitable power unit E.

The construction of the hopper and drier are shown clearly in Figure 2. Fuel delivered to the hopper H is fed by suitable means, as the screw 1, to a distributing means centrally positioned within the drier D. The distributing means as shewn herein consists of a central pot 10 to which the fuel is delivered from below by the screw 1. The pot 10 is non-rotatable. Beneath its edge or lip 11 we position a rotative table 20 formlng a part of the drier D. This table 1s positioned to catch the fuel which is forced over the lip 11 of the pot and to throw it centrifugally outward. It may be inclined upward slightly as shown, if desired, to facllitate construction of the device.

Rotating with the table 20 is a drum 2. This drum receives the fuel which is thrown thereagainst by the table 20 and rotates it at asufici'ent speed to cause this fuel to. adhere thereto centrifugally.

a a Means are provided within the drum 2 for elevating Latc es this fuel and for spreading it in a thin film over the inner surface of the drum 2. The most suitable form of elevating means is a screw. 15 or certain reasons, principally on account of the dificulty of producing an even and regular current of air the'rethrough, a continuous screw is not desirable and we have, therefore, shown a series of interrupted screw elements 22, which we employ for elevating the fuel film. Incidentally these elements 22 agitate the fuel in the film,

the better to expose it to the current of drying air, the course of which is shown by arrows in Figure 2.

Theoretically the screw e'lements22 might be stationary within the drum 2, but practically, in order to cause the fuelto adhere to the drum 2 with a constant force, it is necessary to rotate this at a considerable and constant speed, and it would be undesirable to cause so rapid a feed as would be obtained with stationary screw elements, no matter how fine a pitch might be employed therewith. Moreover there is a pract1cal limit to the fineness of pitch which may be employed with these screw elements. For the reasons outlined, therefore, we prefer that the screw elements 22 be rotated within the drum 2. They are conveniently mounted upon an inner drum 21 and rotate in the same direction as the drum 2; otherwise the effect of stationary screw elements to speed up the rate of feed would be increased to such an extent that effective drying of the material, in a practical device, could not, be accomplished. Tf thesescrew elements were rotated at the same speed as the drum 2, no feed would result. They must, therefore, rotate at a difierent speed, and-preferably at-slower speeds than the drum 2, in order to efiect an advance of the fuel film. However, it is to a large extent immaterial whether the screw elements 22 rotate faster or slower than the drum 2. By rotating them slower the amount of vibration is reduced, and certain advantages of construction and operation are obtained.

The screw elements themselves are spaced about the drum 21, preferably in three series, an element in each succeeding series being adapted to advance the film one-third of the total pitch. In the form as shown in Figure 3 the outermost portion 23 is of relatively low pitch and is of sufiicient depth to project close to the inner surface of the drum 2, to enga e the thin'fuel film adhering thereto. n inner portion 24 which may or may not be formed integral with the portion 23, is not intended to engage the fuel film,.but serves as a fan element to advance the current of drying air over the fuel film. The fuel is ejected centrifugally into the fixed hopper F at the upper end of drum 2 through openings 27.

The operating connections are shown Figures 1, 2, 4 and 5. All parts may be driven from the main shaft 3 through the power unit E. In the arrangement shown the drum 2 is driven by a pair of bevel gears and a grooved friction wheel 31 engaging a similar friction wheel 25 upon the table 20. The inner drum'21, carrying the screw elements, has secured upon its shaft a friction disk 26 with the face of which is engageable the periphery of a friction disk 32, rotative with and slidable upon the shaft 3 to vary the speed of rotation of the inner drum. Evidently the relative speeds of rotation of the two drums might be varied in some other manner, one manner being merely the reverse of that described by varying the speed of rotation of the outer drum 2. This, however, is disadvantageous, as it varies the constant centrifugal force, which should be maintained.

The feed screw 1 has mounted upon the end of its shaft 12, a grooved friction disk 13, with which is engaged an idler disk 14, which in turn engages a grooved friction disk 33 secured upon the shaft 3. Means are provided for varying the rate of feed of fuel by the screw 1 and the lever con trolling these means may be connected with the control lever for the friction disk 32 in order that the feed of fuel through the drier D may be varied simultaneously with the variation of the rate of feed of fuel to the drier. I

The means which we have shown for varying the rate of feed of the screw 1 includes a link 15 fixedly connecting the shafts of the friction disks 14 and 33. An eccentric 16 rotates with the disk 14 and the eccentric rod 17 is reciprocable within a block 18 carried by an end of a lever arm 41, which is adapted to be adjustably fixed in position. A spring 19 operates to project the eccentric rod 17 from the block 18. A

washer 19' is secured upon the outer end of sition owing to the fixed adjustmeht of the B control arm 41. If the block 18 is positioned so that it maybe contacted by the shoulder 17, the disk 14 is, during the period of contact, forced from engagementwith the disk 13 and the drive of the screw 1 is interrupted. By adjusting the position of the lever arm 41 the feed of the screw 1 may be varied in this manner by any amount from zero to feed during the entire rotation of the disk 14. Other suitable means may be employed for accomplishing the same result, such as a common ratchet device.

A control lever 42 is pivoted at 43 and engages a yoke 44 connected with the friction disk 32 to argust the position of the accomplished through .a link 49, which may be provided with a .turn buckle 49' or other means for adjusting its effective length, and which is adapted to be secured to an arm 45. We provide a series of holes 46 in the arm 45 to which the end of the link 49 may be secured, in this manner varying the rate of change of feed ofthe screw 1 and inner drum 21, for a given throw of the control arm 4 which operates the arm 45 and also the arm 47 in which the lever 41 is secured. .A quadrant 48 may be employed to hold the control arm 41in a given position.

Referring again to the drier D, drying air is fed into the fuel receiving hopper F through the intake pipe I and passes thence through openings 27 into the space between the outer and inner drums attheir upper ends. It is then brought downward by the combined action of fan elements 24 and the fans 29 and 29, and passes through openings 28 at the lower end of the inner drum 21, and is then sucked upward by fans 29 and 29', the former rotating withv the inner drum and the latter with the outer drum. Preferably these fans have progressively slightly increased pitches in order to increase .the suction progressively throughout the course of the air. The air is led from the stationary head 20' by means of the outlet pipe 0, as has been described.

.It will be seen that the course of this drying air is counter to the direction of feed of the fuel through the drier. This direc-v &

tion might, however, be reversed if desired,

but that described is the preferable arrangement. The fuel film, afterbeing elevated through the drum 2, is thrown centrifugally therefrom through the openings 27 into the hopper F, as described above, and is led by the conduit C to the pulverizer P. A portion of the air, an excess of which is admitted through the pipe I, accompanles the fuel through the hopper F and conduit C to the pulverizer P, and thence through the suction means J to the burner This provides a carrying medium for the pulverized fuel and a positive circulation therefor, and acts to dry the coal further during and after pulverization.

The form of pulverizer which we prefer to employ comprises a disk or table 5 "rotating with-in a casing 50 and having thereon upstanding hubs 51. The hubs 51 may be rotatively mounted upon studs'52, and upon these hubs are pulverizing rings 13 which have a central opening 54 somewhat larger in diameter than the hubs 51. Revolving. the disk 5 rapidly forces-the rings free thereof.

, opening (riot shown).

through bevel gears 30. Fuel is delivered through a central intake pipe 56, to which it is delivered from the conduit C, to the center of the disk 5, and is then thrown outward into the path of the rings 53 to be ground between these rings and the track 55. Baflies 57 are provided to direct downward large particles of fuel which may be thrown from the pulverizing-rings before being ground. The pulverulent fuel is led out through an outlet pipe 58 communicating with the suction means indicated 'at J.

In order to keep particles of fuel and fuel dust from the bearings of disk 5, we provide fanelements 59 upon the lower side of'the disk 5 which force the air between the edge of the table 5 and the casing 50. This current of air always moving toward the material being pulverized, blows out particles of coal dust and keeps the clearance space between the disk and track k Similar means may be employed in the drier, if desirable or necessar idfter being pulverized the fuel may be handled conveniently by suction means. Those which we have indicated at J comprise a steam or air nozzle 6 to which dry steam or air is delivered through a suitable control valve 60, and pointing through a suction jet 61 directed down the conduit ,K to the burner B. The pulverized fuel and air from the coal intake is sucked through the pipe 58 by the suction of the steam or air. passing through the jet 61 and is mingled with the steam. This provideda heated mixture which is highly combustible when mixed with the proper amount of additional air at the furnace, which is admitted throu h a suitable draft urther, if drying air, steam, or gases are employed at this nozzle, considerable additional drying of the pulverized fuel is efiected.

The additional air is supplied at the burner B where the mixture of steam, air, and pulverized fuel is delivered to the furnace A. The burner itself may be simply formed as a Venturi tube 7 which has its outlet directed into and preferably projecting slightly into the furnace A. The tube 7 at its outlet end may be surrounded by a casin 71 which has openings 72 through which hot gases from the furnace may be drawn in to mingle with the mixture discharged from the burner to heat the same to facilitate ignition. The openings 72 are preferably rearwardly of the outlet openings 70 of the tube 7, which is in turn rearwardly of and spaced from the outlet opening 73 of the casing A lip 74 projecting laterally from the casing 71 serves to direct the hot gases to the opening 72 rather than directly to the discharge opening 7 3 l of the casing and in this manner it serves filtrates to increase the combustible edect of these heated gases. The fuel mixture is, in the manner described, heated up to the ignition point and forms a very hot flame immediately upon its projection from the casing 71.

lit is believed that "the operation of the device will "be clear from the above description of the construction and operation of the several parts and from an inspection of Figure 1. We shall not, therefore, further describe the operation of the machine in general. Regardin the pulverizer and pulverized fuel-handling means, it should be noted that a considerable drying efi'ect is attained by the use of a drying agent, such as warm air, as a vehicle in the" progress of the fuel from the drier D, through the pulverizer P, and through the several conduits '0 and K. The object is to deliver the fuel to 'the burner in as dry a state as possible, although accompanying moisture contained in the air is not objectionable. Drying is naturally more readily effected with pulverized than with granular material, although the fuel should be dried while in the granular form to permit efiicient operation of the pulverizer. This method of handling the fuel and additionally drying it throughout our process W? consider a part of our invention.

We have described a process in which three drying operations are employed: the

prising a rotatable drum and a concentrically mounted elementrotatable therein at a slower speed than said drum, said element having vanes thereon extendin towards the drum, and inclined downward y in the direction of its rotation.

'2. An elevator for a granular material comprisinga rotatable drum and diderentially rotatable, concentrically mounted screw elements therein, and means for varying the relative speeds'of rotation of said arts.

3. combination, an elevator for granular material comprising a rotatable drum, internal means forv advancing material therethrough, means for feeding material to said drum, and meansfor simultaneously varying the quantity of material fed to said drum and the rate of feed of material passing through and discharged from said drum.

4. An elevator for granular material comprising arotatable drum and concentrically mounted screw elements; rotatable therein in the same direction,- and means for varying the relative speed of rotation of said parts from equal to speeds where the drum rotates the faster.

5. A drier for granular material comprising a rotatable drum, means for advancing a film of material centrifugally adhering thereto, means for guiding a current of drying air over said film of material 6. A drier for granular material comprising a rotatable drum, means for advancing and agitating a film of material centrifugally' adhering thereto, and means for guid ingia current of drying air over said film of material.

7. A drier for granular material comprising a rotatable drum, means for advancing a film of material centrifugally adhering thereto, and means for producing a current of drying air over said film counter to its direction of feed.

8. A drier for granular material comprising a rotatabledrum, screw elements ro-. tatable therein to advance a film of material centrifugally adhering to said drum, and means for producing a current of drying air over said film.

9. A drier for granular material comprising interrupted screw elements, a drum rotatable thereabout, whereby a film of material centrifugally adhering to said drum is moved to be advanced and agitated, and means for producing a current of drying air over said film.

10. A drier for granular material comprising interrupted screw elements, a drum rotatable thereabout, whereby a film of material centrifugally adhering to said drum is moved to be advanced and agitated, and means rotatable within said drum for producing a current of drying air over said film counter to its direction of feed.

11. A drier for granular material comprising a rotatable drum, feed members rotatable therein at a different speed to advance a film of materal centrifugally adherin to said drum, said feed members being a so adapted to reduce a current, of drying air over said 12. A drier for granular material comprising a rotatable drum, feed members rotatable therein at a different speed to advance a film of material centrifugally adheiing to said drum, said feed members being also adapted to produce a current of drying air over said film in the. opposite direction to the feed of said material.

13. A drier for anular material comprising a rotatable rum, and two-part feed members rotatable therein at a difierent speed, outer part of said feed-members acting to advance a. film of material centrifugally adhering to said drum, and their hering to said drum, and their inner part being clear of the film and positioned to produce a current of drying air'(over said film in a direction counter to the direction of feed of the material. L

15. A drier for granular material comprising a rotatable drum, inclined feed members rotatable therein at a .slower speed and engaging a film "of material centrifugally v adhering to said drum, and fan blades rotatable therein in the same direction, and

inclined in the same direction as said 'feed members to prodiice a current of drying air over said film of material in a direction counter to the direction of feed thereof.

16. A drier for granular 'material comprising a rotatable drum, inclined "feed members rotatable'therein at a slower speed, and engaging a film of material centrifugally adhering to saiddrum, and fan blades rotatable therein in the same direction, at the same speed, and inclined in the same direction as said feed members to produce a current of drying air over said film vof material ina direction counter to the direction' of feed thereof.

17. In a pulverized-fueleburning apparatus, in combination, a central fuel-distributing means, a rotating drum having a table rotatable beneath the edge of said distributing means, and means for elevatin aof fuel centrifugally adhering to sai drum. 18. In a pulverized-fuel-burning. apparatus, in combination, a central distributing means, a rotating drum having a table rotatable beneath the edge of said distributing means, means for elevating a film of fuel centrifugally adhering to said drum, the upper end of said drum having outlet open,- ings, and a non-rotative fuel receiver surrounding such outlet openings. 3 A

19.: In a pulveriZed-fuel-burning apparatus,a drier comprising, in combmation, a central distributing means, a rotatable drum having a table rotatable beneath the edge of the distributing means, an internal drum rotatable within the first drum, means carried thereby for elevating a. film of'fuel centrifugally adhering to said first drum, the upper end of said first drum and the lower end of the internal drum having openings therethrough, a 'non-rotative fuel receiver surrounding the openings in said outer drum, said openings in the outer and inner drums acting as air passages to guide drying air over said film of fuel.

20. In a pulverized-fueLburning apparatus, in combination, a central pot, means for delivering granular fuel to said pot, a rotating drum having a table rotatable beneath the lip of said pot, and means for elevating a film of fuel centrifugally adhering to said drum. I

21. In a" pulverized-fuel-burning apparatus, in combination, a central pot, a feed screw for delivering fuel into and over the lip of said pot, a rotating drum having a table rotatable beneath the lip of said pot, and means for elevating a film offuel cen- "trifugally adhering to said d.

22. In a pulverized-fuel-burning apparatus, in combination, .a rotatable drum, screw elements rotatable to advance fuel therein, means for varying therelative rotational speeds of said elements, means for feeding fuel into said "drum, and means operable with said first j s cod-changing means fq rvarying-the rate 0 feed of said latter means;

23. In a pulverized-fuel-burning apparatus, in combination, a drum rotatab e at a fixed speed, screw elements rotatable therein to advance fuel centrifugally adhering to said drum, means for varying the speed of rotation of said screw elements relative to the drum, means for feeding fuel into said drum, and means operable with said first speed-changing means for varying the rate of feed of said latter means. i

24. In a pulverized-fuel-burning apparatus,'in combination, a drum rotatable at a fixed speed, screw elements rotatable therein to advance fuel centrifugally adherin to said dnnnl, means for varying the spec of rotation of said screw elements relative to the drum, means for feedmg fuel into said drum, means operable with said first speed-changing means for varying the rate of feed of said latter means, and means for varying the relative rate of change of speed in the respective speedchanging means.

25. In a pulverized-fuel-burning apparatus, in combination, a continuouslydriven drum rotatable at a constant speed,

screw elements rotatable to advance fuel adhere thereto, and interrupted screw eletnents rotatable therein at a difl'erent speed and engaging the materialto advance it.

27. An elevator for, granular material comprising an upright drum, rotatable at a speed to cause the material to centrifugally adhere thereto, and interrupted inclined screw elements rotatable therein at a different speed and engag the material to advance it, said screw elements bein each axially, spaced from the preceding e ement by the height of the latters inclination.

Signed at Seattle, Kin County, Washington this 4th day of Fe ruary,l91l,

PAUL O. MULLIGAN. I FREDERICK S. lBltlIN'I@Nz EUELMUTH W. SClHlll/IITZ.

Kill 

